Aren't there plenty of preamps that would work?
I have Sansamps, A mizpad 9, fishman pre-amps, etc. I use most for preamps for instruments, like uprights, or acoustic guitars with a pieso and no pre-amp. DOD makes one the size of a guitar pedal with controls that let you vary the signal.

The Mixpad 9 has stereo ins and outs, with pots.

Just a suggestion..

Russ